A flange portion of a common through shaft is integrated with the shaft. In a case where the through shaft is being mounted to axle housing, since a lock nut has already been fitted on the shaft, operations become difficult due to the narrow space. As a result, a specially hook-shaped wrench has to be is used to tighten the nut little by little, which leads to low efficiency, and the torque requirement of the assembly process cannot be met. Finally, it is still necessary to realize locking by means of punching and riveting, which makes the assembly requirement of high-quality driving axle hard to be met.